While reading a Wiki page about pragmatics and presuppositions, I came upon this explanation:

Is there a professor of linguistics at MIT? » Either there is a professor of linguistics at MIT or there isn't.

I can see the question presupposes the polarity; still, I don't see what's wrong to make such a presupposition. Isn't it true either there is such a professor or no? Or, does it presuppose something else rather than the polarity, like "linguistics at MIT"?

Would someone please help explain: (i) what's been presupposed in addition to the polarity; and (ii) what are other possibilities other than there is such a professor or no.

Thank you very much for your time!!


3 Answers 3


What's being presupposed in addition to the polarity

Considering the intent of that particular example, I believe that this sentence is simply explicitly highlighting the trivial, perhaps tautological presupposition to illustrate that even though we might not think about it, such sentences imply the polarity and if we want to be careful, that should be considered. Also, the "storytelling" function of that presupposition example is in contrast with the following two examples of more substantial presuppositions.

Other possibilities

However, if we go into detail, I can imagine situations where the true answer to questions in the style of "is there a professor of linguistics at [institution]" is not yes, not no, but "it's complicated", where the exact answer depends on nuances of how you interpret the question. Perhaps at this very moment professors are home and not physically "at" the institution, perhaps they have more specific titles e.g. professor of phonology so they have de facto professors of linguistics without having anyone with the title "professor of linguistics", etc.

So perhaps the main presupposition is that the categories used are well-defined with strict boundaries - that there is some clear unambiguous criteria that can be used to evaluate, for example, if a particular person is "professor of linguistics at MIT". Law of excluded middle is tricky to apply without very formal definitions - in this case we can perhaps dismiss it as trivial, but not in the general case.

For example, consider a somewhat politically loaded question of "Is there a woman in this room?" in the situation where the room contains a transgender person; the question carries an automatic presupposition that the question has a yes/no answer, which implies a presupposition that the categories used (i.e "woman") have a clear boundary and a common definition shared by all participants in the discourse - which isn't always true. So even if a sentence just presupposes polarity, that might be a quite strong presupposition in some cases.


I think your claim is that the statement "either there is a professor of linguistics or there isn't" is a tautology and therefore not a supposition at all. And I think you're right. Unless we want to dive into the philosophy of existence, "X exists" is a true or false statement. If we call that statement P, then from a standpoint of formal logic, "P or not P" is a tautology since it is always true: so P is meaningless and not a supposition.

I think the real presupposition in your sentence is "MIT exists." But this is not what the Wikipedia page presents.

  • 2
    Compare with the question "Is the king of England bald?" (England doesn't have a king, at the time of writing, but the question presupposes that the king exists). I agree the Wikipedia example is poor and confusing.
    – alephzero
    Apr 16, 2021 at 12:26
  • Maybe the intention is that "MIT exists" is part of "Either there is a professor of linguistics at MIT or there isn't"? Contrast "If Monster University exists, either there is a professor of linguistics there or there isn't" with "Either there is a professor of linguistics at Monster University or there isn't". The former is (vacuously) true, while the latter seems hard to assign a truth value to.
    – ruakh
    Apr 16, 2021 at 17:15
  • "P or not P" is only tautological in classical logic, which assumes the law of the excluded middle. Obviously, we all implicitly accept the law of the excluded middle in everyday life and ordinary language, so this is maybe a little pedantic, but I think it's worth acknowledging that it is not a necessary logical truth. If one is open to the fact that the law of the excluded middle may or may not hold, then it is a presupposition of the sentence in question.
    – d_b
    Apr 16, 2021 at 17:21
  • @d_b Hence my comment on the philosophy of existence... I said that in the hopes of avoiding exactly this kind of nit-picking ;)
    – TypeIA
    Apr 16, 2021 at 18:26

I didn't see any indication on the linked page that that presupposition has anything wrong with it. The page simply points out that a presupposition is implied by the question, and will be recognized by the hearer of the question. It is a yes/no question.

  • 2
    I think the point of the question was not about the "wrongness" of the presupposition, but whether the alleged presupposition is actually a tautology and therefore not a supposition at all. And I agree. I think the real presupposition in that sentence is "MIT exists," and this is not what the Wikipedia page discusses.
    – TypeIA
    Apr 16, 2021 at 6:04
  • 1
    I've edited the question to make my point more explicit so Jack's answer was to actually address the previous version of my question. Sorry about the confusion.
    – Lenny
    Apr 16, 2021 at 8:19

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